late 13c., from Anglo-French duete, from Old French deu "due, owed; proper, just," from Vulgar Latin *debutus, from Latin debitus, past participle of debere "to owe" (see debt). Related: Duties. The sense of "tax or fee on imports, exports, etc." is from late 15c.; duty-free as a noun is attested from 1958.

Old English dweorh, dweorg (West Saxon), duerg (Mercian), "very short human being," from Proto-Germanic *dweraz (source also of Old Frisian dwerch, Old Saxon dwerg, Old High German twerg, German Zwerg, Old Norse dvergr), perhaps from PIE *dhwergwhos "something tiny," but with no established cognates outside Germanic. The mythological sense is 1770, from German (it seems never to have developed independently in English).

Whilst in this and other ways the dwarfs do at times have dealings with mankind, yet on the whole they seem to shrink from man; they give the impression of a downtrodden afflicted race, which is on the point of abandoning its ancient home to new and more powerful invaders. There is stamped on their character something shy and something heathenish, which estranges them from intercourse with christians. They chafe at human faithlessness, which no doubt would primarily mean the apostacy from heathenism. In the poems of the Mid. Ages, Laurin is expressly set before us as a heathen. It goes sorely against the dwarfs to see churches built, bell-ringing ... disturbs their ancient privacy; they also hate the clearing of forests, agriculture, new fangled pounding-machinery for ore. ["Teutonic Mythology," Jacob Grimm, transl. Stallybrass, 1883]

The shift of the Old English guttural at the end of the word to modern -f is typical (compare enough, draft). Old English plural dweorgas became Middle English dwarrows, later leveled down to dwarfs. The use of dwarves for the legendary race was popularized by J.R.R. Tolkien. As an adjective, from 1590s.

Related to Old English gedweola "error, heresy, madness." Sense shifted in Middle English through "hinder, delay," to "linger" (c. 1200, as still in phrase to dwell upon), to "make a home" (mid-13c.). Related: Dwelled; dwelt; dwells.

1670s, from Latin dyad-, stem of dyas, from Greek dyas "the number two, a group of two," from duo "two" (see two). Specific sense in chemistry ("a bivalent element") is by 1865; also used in biology, poetics, mathematics. Related: Dyadic.

Old English deagian "to dye," from the source of dye (n.). Spelling distinction between dye and die was not firm till 19c. "Johnson in his Dictionary, spelled them both die, while Addison, his near contemporary, spelled both dye" [Barnhart]. Related: dyed. For dyed in the wool (or grain) see wool (n.).

1931, American English, perhaps a shortening of morphadike, dialectal garbling of hermaphrodite; but bulldyker "engage in lesbian activities" is attested from 1921, and a source from 1896 lists dyke as slang for "the vulva."

[T]he word appears first in the long forms, bulldiker and bulldyking, both used in the 1920s by American blacks. No African antecedents have been found for the term, however, which leads to the possibility that this is basically just another backcountry, barnyard word, perhaps a combination of BULL and DICK. [Rawson]

1817 as a term in philosophy; 1827 in the sense "pertaining to force producing motion" (the opposite of static), from French dynamique introduced by German mathematician Gottfried Leibnitz (1646-1716) in 1691 from Greek dynamikos "powerful," from dynamis "power," from dynasthai "to be able, to have power, be strong enough," which is of unknown origin. The figurative sense of "active, potent, energetic" is from 1856 (in Emerson). Related: Dynamically.

1882, short for dynamo-machine, from German dynamoelektrischemaschine "dynamo-electric machine," coined 1867 by its inventor, German electrical engineer Werner Siemans (1816-1892), from Greek dynamis "power."

metric unit of force, 1873, from German use of Greek dynamis "power" (see dynamic (adj.)); perhaps also influenced by French dyne, which had been proposed c. 1842 as a unit of force in a different sense.

Very productive in ancient Greek, where it could attach even to proper names (such as dysparis "unhappy Paris"); its entries take up nine columns in Liddell and Scott. Among the words formed from it were some English might covet: dysouristos "fatally favorable, driven by a too-favorable wind;" dysadelphos "unhappy in one's brothers;" dysagres "unlucky in fishing;" dysantiblepos "hard to look in the face."

The French psychologist Albert J. Carnoy gave an extensive definition in his study Le Science du Mot, which in translation runs: "Dysphemism is unpitying, brutal, mocking. It is also a reaction against pedantry, rigidity and pretentiousness, but also against nobility and dignity in language" (1927, xxii, 351). [Geoffrey L. Hughes, "An Encyclopedia of Swearing," 2006]

element, obtained 1906 from an earth discovered in 1886, the last to be extracted from the complex earth called yttria, and named dysprosia in reference to the difficulty of obtaining it, from Greek dysprositos "hard to get at, difficult of access," from dys- "bad" (see dys-) + prositos "approachable." With metallic element suffix -ium.